A multiscale framework for polymer modeling applied in a complex fluid flow

Understanding polymer dynamics under shear flow is crucial for studying their rheological behavior in diverse applications. However, conventional micro analyses provide limited insights into polymer elongation and conformation. To address this, we propose a hybrid model combining the Lattice Boltzmann method and Langevin Dynamics technique, which captures the multiscale nature of polymer dynamics. Using the coarse-grain bead-spring method, we optimize computational efficiency and model polymers as chains with specific mass and charge. Our hybrid model integrates Navier-Stokes equations with external drag force modified based on segment velocities from Brownian Dynamics simulations.

In our study, we investigated the effects of chain structure and solvent properties on polymer solutions under shear flow through numerical simulations. We observed that in high shear rate flows, a viscous solvent promotes polymer elongation, while low shear rate flows lead to chain insolubility in the base oil. Longer chains have a greater overall impact on the fluid due to increased contact points with the solvent. The size of the polymer coil over time is influenced by shear rate, chain length, and solvent viscosity. Moreover, solvent density, particle mass, and radius locally affect fluid flow. The higher viscosity fluids result in amplified hydrodynamic and random forces acting on the chains. These findings have implications for applications involving polymer additives that alter the properties of the host solvent in natural and artificial processes. Our study represents an initial step towards a comprehensive understanding of polymer dynamics, taking into account the diverse factors that influence them.